Conventionally, there has been a light-emitting device in a rod-like structure having a size of the order of nanometers in which a rod-like core portion made of a compound semiconductor and a cylindrical shell portion made of a compound semiconductor surrounding the core portion form a heterostructure (see, for example, JP-A-2008-235443). In the light-emitting device, the core portion itself serves as an active layer, and electrons and holes injected from the outer peripheral surface recombine in the core portion to emit light.
In the case where using a manufacturing method similar to that for the above light-emitting device, a rod-like light-emitting device is manufactured that has a core portion made of an n-type semiconductor and a shell portion made of a p-type semiconductor and in which electrons and holes recombine at a pn junction between the outer peripheral surface of the core portion and the inner peripheral surface of the shell portion to emit light, the core portion is exposed only on its both end surfaces, and therefore there arises a problem in that connecting the core portion and an electrode is difficult.
There has been a method of manufacturing a rod-like light-emitting device. In the method, after a flat first polarity layer is formed on a substrate, a plurality of light-emitting nanoscale rods, which corresponds to the active layer to emit light, are formed on the first polarity layer, and further a second polarity layer wrapping around each of the rods is formed (see, for example, JP-A-2006-332650). In this rod-like light-emitting device, light is emitted from the plurality of rods serving as the active layer.
However, the above rod-like light-emitting device is used together with the substrate on which the plurality of nanoscale rods are provided, and is subjected to the constraints of the substrate when incorporated into an illuminating device or a display device. Therefore, the rod-like light-emitting device has a problem in that there is less freedom in installing into an apparatus.
Furthermore, a light-emitting apparatus including the above rod-like light-emitting device has a problem in that the light-extraction efficiency decreases because, under the condition in which the plurality of rods erect on a substrate, most light is emitted laterally to be absorbed into the adjacent rods. In the above rod-like light-emitting device, the plurality of rods erect on the substrate, and therefore there is a problem in that the heat dissipation efficiency is poor.